Morphostructural and immunohistochemical study for evaluation of nano‐TiO2 toxicity in Armadillo officinalis Duméril, 1816 (Crustacea,Isopoda, Oniscidea)

Invertebrates are precious organisms in order to study environmental pollution. In particular, they appear to be suitable as a bioindicator species for pioneer ecotoxicity studies on new xenobiotics such as nanoparticles. In fact, they are able to absorb nanomaterials scattered in the environment in different ways and it's known the compartmentalization of nano‐sized contaminants in selected tissues and intracellular organelles. Titanium dioxide represents the most used nanoparticulate, destined to become probably ubiquitous in the environment. Recently, some research has been published on the toxic potential of nano‐TiO₂ in several animal species. Among all invertebrates, Oniscidean Isopods are the only taxon of Crustaceans that has become completely terrestrial, known as excellent bioindicators and bioaccumulators. They have a digestive gland, the hepatopancreas, which is the location of election for the accumulation of pollutants. For this reason, they are considered efficient animal models to ecological studies. For this study, we collected Armadillo officinalis from Natural Oriented Reserve of “Vendicari” (Sicily, Italy), to evaluate the toxicity of titanium dioxide (TiO₂) on their hepatopancreas, after a short period of exposure. We conducted morphostructural and immunohistochemistry assays. The results suggested a great capacity of the species of bioaccumulation of nanoparticles in the hepatopancreas, where a strong positivity to the metallothioneins was highlighted. Our study confirms that Oniscidean Isopods, in particular Armadillo officinalis, proved to be an appropriate indicator of pollution in terrestrial ecosystems from nanoparticles.     

Effects of trace metal elements on ultrastructural features of hepatopancreas of Armadillidium granulatum Brandt, 1833 (Crustacea,Isopoda)

This study was conducted to compare metals bioaccumulation in the terrestrial isopod Armadillidium granulatum collected from Ghar El Melh lagoon. We focused on recognizing the effects of trace elements on hepatopancreas functional role. To this end, isopod specimens were exposed for 3 weeks to sediments contaminated with cadmium, copper, zinc, mercury, and nickel. Three concentrations were used in duplicate for each experimental condition. At the end of the experiment, metal body burdens were determined using flame atomic absorption spectrometry. Results of the bioaccumulation factor (BAF) showed that the species A. granulatum was classified as a Cu macroconcentrator (BAF > 2) and a Zn deconcentrator (BAF < 2). Dose dependent morphological and histological changes were observed in the hepatopancreas cells using transmission electron microscopy. The predominant features were: microvillus border disruption, condensation of the cytoplasm with increasing endoplasmic reticulum, mitochondria, lysosomes and granules that accumulated metals in B and S cells. The number of lipid droplets decreased especially after Cd, Zn, Hg, and Ni treatments. This study demonstrated that the terrestrial isopod A. gramulatum could be a good indicator of soil metal contamination.     

Physiological and histopathological responses of Porcellio laevis (Isopoda,Crustacea) as indicators of metal trace element contamination

This study was designed to assess the impact of the mixture of cadmium (Cd) and zinc (Zn) on the bioaccumulation and the ultrastructural changes in the hepatopancreas of Porcellio laevis (Latreille, 1804) after 4 weeks of exposure to contaminated Quercus leaves under laboratory conditions. For each metal, four concentrations were used with four replicates for each concentration. Metal concentrations in the hepatopancreas and the rest of the body were determined using atomic absorption spectrometry. From the first week until the end of the experiment, a weight gain in P. laevis was observed particularly between the first and the end of exposure from 93.3 ± 18.22 mg fw to 105.22 ± 16.16 mg fw and from 106.4 ± 22.67 mg fw to 125.9 ± 23.9 mg fw for Mix1 and Mix4, respectively. Additionally, the determined metal trace elements (MTE) concentrations in the hepatopancreas were considerably higher compared to those in the rest of the body and seem to be dose‐dependent. Using transmission electron microscopy (TEM), some alterations were highlighted in the hepatopancreas. The main observed alterations were (a) the destruction of the microvilli border in a considerable portion of cells, (b) the increase of the lipid droplets with different shapes and sizes, (c) the increase in the number of the mitochondria, and (d) the appearance of TE in the form of B‐type granules. The obtained results confirmed the ability of P. laevis to deal with high amounts of MTE, suggesting its possible use in future soil's biomonitoring programs.     

Focused ion beam/scanning electron microscopy studies of Porcellio scaber (Isopoda, Crustacea) digestive gland epithelium cells

The focused ion beam (FIB) was used to prepare cross sections of precisely selected regions of the digestive gland epithelium of a terrestrial isopod P. scaber (Isopoda, Crustacea) for scanning electron microscopy (SEM). The FIB/SEM system allows ad libitum selection of a region for gross morphologic to ultrastructural investigation, as the repetition of FIB/SEM operations is unrestricted. The milling parameters used in our work proved to be satisfactory to produce serial two-dimensional (2-D) cuts and/or three-dimensional (3-D) shapes on a submicrometer scale. A final, cleaning mill at lower ion currents was employed to minimize the milling artifacts. After cleaning, the milled surface was free of filament- and ridge-like milling artifacts. No other effects of the cleaning mill were observed.     

Egg envelopes of Armadillidium vulgare (Latreille, 1804) (Crustacea,Isopoda Oniscidea): Ultrastructure and lectins binding

The ultrastructural study carried out on (a) oocytes of Armadillidium vulgare during vitellogenesis, (b) mature eggs taken from the ovaries during the parturial moult of the posterior half of the body, and (c) fertilized eggs collected within a few hours of their release into the brood pouch, has clearly demonstrated that before the fertilization the chorion is the only envelope present in the egg of oniscidean isopods. In the mature eggs, the chorion appears as a uniformly electron‐dense lamina, about 0.4–0.5 µm thick, which does not show any specialized area. A second envelope, described by other authors as vitelline envelope, is formed above the oolemma only right after fertilization and appears separated from the chorion by a space full of liquid. The ways in which the genesis of this envelope is realized are not yet clear; it could be interpreted rather as a fertilization membrane. The investigations carried out with the aid of a battery of FITC‐lectins have highlighted the presence at the chorion surface of unfertilized eggs of various saccharide residues distributed in uniform way. No significant change was observed in the pattern of lectins binding to the chorion of eggs taken from the brood pouch, thus demonstrating how, after the fertilization, no significant rearrangement in the distribution of saccharide residues present on the egg surface occurs in A. vulgare. The ways in which, therefore, the recognition, the binding and the entry of the peculiar sperm of oniscidean isopods into the egg occur, still remain all to be deciphered. Microsc. Res. Tech. 79:792–798, 2016. © 2016 Wiley Periodicals, Inc.     

The induced damage in the hepatopancreas of Orchestia species after exposure to a mixture of Cu/Zn—An ultrastructural study

The hepatopancreas of crustaceans species has been recognized as an essential target organ to assess trace elements' effects. Due to its dynamic and capability of detoxifying trace metal, this organ often indicates distinct pathological disturbances. In the present work, we intend to evaluate the bioaccumulation of trace metal in three Orchestia species (Orchestia montagui, Orchestia gammarellus, and Orchestia mediterranea) living in symmetry in the banks of Bizerte lagoon (37°13′8″N 09°55′1″E) after their exposure during 14 days to a mixture of copper and zinc, and to highlight the effect of these metals on their hepatopancreas ultrastructure using transmission electron microscopy. At the end of the experiment, results showed that the mortality and the body mass varied according to the used nominal concentrations. Significant alterations were noted in all the treatment groups. The degree of these alterations depends on the used concentration, and they are represented especially by the cells remoteness and the border lyses, the reduction of the nuclear volume, the increase in the cytoplasm density with the presence of trace metal in the nucleus as well as in the vacuole, the disorganization and the destruction of microvilli, the condensation of the majority of cellular organelles and mitochondria swelling. Through this study, Orchestia genus could be an attractive candidate for the biochemical study of trace metal toxicity in Tunisian wetlands.     

Morphology,distribution, and abundance of antennal sensilla of male and female macropterous and brachypterous small brown planthopper,Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae)

The antennal sensilla of both genders of macropterous and brachypterous adults of the small brown planthopper, Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) were examined using light and scanning electron microscopy. Scanning electron microscopy revealed seven types of antennal sensilla in adult L. striatellus which were not evenly distributed on all antennal segments. Sensilla chaetica, a sensillum campaniformium and a Böhm bristle were found on the scape. Sensilla chaetica, sensilla trichodea, sensilla placodea which always present as plaque organs, sensilla basiconica and a sensillum campaniformium were present on the pedicel. Three sensilla basiconica and one sensillum coeloconicum containing two sensory pegs were located on the swollen sensory region of the basal flagellum. Pores observed on the surface of s. trichodea and s. placodea suggest these organs probably play a role in olfaction, whereas the aporous s. chaetica with flexible sockets probably function as mechanoreceptors. The aporous s. basiconica with inflexible sockets are probable to be thermo‐hygroreceptors while the Böhm bristle and s. campaniformia may act as antennal proprioceptors. The function of s. coeloconicum remains uncertain. The numerical dominance of antennal olfactory receptors suggests olfaction is an important function of the antenna in L. striatellus. Although a small degree of sexual/wing dimorphism was observed in the numbers of sensilla and in the length and width of antennae and antennal segments, the basic shape and structure of the antennae and antennal sensilla did not differ between the gender or wing form in L. striatellus. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

The effect of vacancies on the annular dark field image contrast of grain boundaries: a SrTiO(3) case study

The analysis of grain boundary structure in high resolution electron microscopy is often hindered by contrast variation within the grain boundary region which is not explained by simple models of the grain boundary structure. Recent work suggests that structural disorder along the beam direction and the presence of vacancies contribute significantly to this effect. One might expect a significant reduction in contrast in a Z-contrast image of a grain boundary would imply that vacancies present must result from the absence of heavier elements. Using a [001](210) Σ5 grain boundary in SrTiO₃ as a test case and first principles structure relaxation to calculate stable defect structures, we show that the reduction in the intensity from fully occupied Sr columns due to the structural distortion resulting from a nearby O vacancy can be as great as that due to introducing a Sr vacancy in the column itself. The effect on energy dispersive X-ray spectroscopy signals is also considered, but found to be smaller than that on Z-contrast images.